The purpose of this study was to examine the effects of aerobic exercise on physiological exercise intensity and the perception of exercise intensity in the young. Fifteen young men ran on a treadmill at subjective exercise intensities of “somewhat hard” and “fairly light” for 3 min each before and after they were subjected to training for 1 month. Subjects adjusted their exercise intensity levels using a speed adjustment button that did not display their running speed. Aerobic exercise for 1 month was conducted for 40 min thrice a week during which the exercise intensity was maintained at 60% VO2 max. Measured parameters included physiological exercise intensity (%) and subjective perception of exercise intensity (%). The former was calculated by relative VO2 during exercise with intensity levels of “fairly light” and “somewhat hard.” The latter was measured based on responses to the question, “what percentage of maximal effort did you exert at the “fairly light” and “somewhat hard” exercise intensities?” Physiological measurements during “fairly light” and “somewhat hard” exercises reflected higher levels of exercise intensity than did the subjects’ subjective perceptions. Neither parameter varied over the month-long study, which suggested that regular exercise did not influence exercise intensity.